group.h

DISPATCH_DECL(dispatch_group);

__OSX_AVAILABLE_STARTING(__MAC_10_6,__IPHONE_4_0)
DISPATCH_EXPORT DISPATCH_MALLOC DISPATCH_RETURNS_RETAINED DISPATCH_WARN_RESULT
DISPATCH_NOTHROW
dispatch_group_t
dispatch_group_create(void);

void
dispatch_group_async(dispatch_group_t group,
    dispatch_queue_t queue,
    dispatch_block_t block);

void
dispatch_group_async_f(dispatch_group_t group,
    dispatch_queue_t queue,
    void *_Nullable context,
    dispatch_function_t work);

long
dispatch_group_wait(dispatch_group_t group, dispatch_time_t timeout);

void
dispatch_group_notify(dispatch_group_t group,
    dispatch_queue_t queue,
    dispatch_block_t block);

void
dispatch_group_notify_f(dispatch_group_t group,
    dispatch_queue_t queue,
    void *_Nullable context,
    dispatch_function_t work);

void
dispatch_group_enter(dispatch_group_t group);

void
dispatch_group_leave(dispatch_group_t group);